fix: improve Playwright browser cache in CI

[Copilot]

The Playwright cache step had three issues: pinned to @main (unstable), used a hardcoded runner path, and set restore-keys identical to key (making it a no-op fallback).

Changes

• actions/cache@main → actions/cache@v4 — stable, versioned pin
• Cache path — /home/runner/.cache/ms-playwright → ~/.cache/ms-playwright
• restore-keys — prefix-only fallback so a Playwright version bump still yields a partial cache hit instead of a cold start

- name: Cache Playwright dependencies
  uses: actions/cache@v4
  with:
    path: ~/.cache/ms-playwright
    key: playwright-${{ runner.os }}-${{ hashFiles('playwrightVersion.mill') }}
    restore-keys: |
      playwright-${{ runner.os }}-

Original prompt

Create a pull request to improve Playwright caching in the GitHub Actions workflow.

Repository: Quafadas/live-server-scala-cli-js
Target file: .github/workflows/ci.yml (on branch main)

Changes requested:

1. Update the Playwright cache step to use a stable actions/cache version tag (v4) instead of @main.
2. Change the cache path from a hard-coded /home/runner/.cache/ms-playwright to ~/.cache/ms-playwright.
3. Fix restore-keys so it provides a useful fallback. Current restore-keys is identical to the key. Update it to restore by prefix, e.g.:
   • key: playwright-${{ runner.os }}-${{ hashFiles('playwrightVersion.mill') }}
   • restore-keys: |
     playwright-${{ runner.os }}-
4. Keep the key format as-is (still based on hashFiles('playwrightVersion.mill')) unless the implementation requires small adjustments for correctness.

Acceptance criteria:

• Workflow YAML remains valid.
• Cache step correctly restores an older Playwright cache when the exact key is missing.
• No other functional changes to the workflow besides the caching improvements.

Reference URL: https://github.com/Quafadas/live-server-scala-cli-js/blob/main/.github/workflows/ci.yml

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: is playwright here correctly cached?

Assistant: No — it’s partially right, but it’s not robust, and the cache key logic is a bit off.

What you’re caching

You cache:

path: /home/runner/.cache/ms-playwright

That is the correct directory for Playwright browser downloads on Linux runners (the “ms-playwright” browser cache). So the path choice is good.

What’s wrong / suboptimal

1) restore-keys is ineffective as written

You have:

key: playwright-${{ runner.os }}-${{ hashFiles('playwrightVersion.mill') }}
restore-keys: |
  playwright-${{ runner.os }}-${{ hashFiles('playwrightVersion.mill') }}

That restore-keys entry is identical to the key, so it won’t ever fall back to “closest match”. If the exact key doesn’t exist, it restores nothing.

Usually you want a prefix fallback, e.g. playwright-${{ runner.os }}- so that if the version file changes, you can still restore an older browser cache.

2) Cache key depends on playwrightVersion.mill existing + actually changing

If playwrightVersion.mill:

• doesn’t exist,
• isn’t what actually controls the Playwright version used by just setupPlaywright,
• or isn’t updated when Playwright changes,

…then your cache key won’t track the real browser revision, and you can end up restoring a cache that doesn’t match what Playwright expects (which can cause Playwright to re-download anyway).

3) Your install step may not use that cache unless it downloads to that path

Whether this cache works in practice depends on what just setupPlaywright does:

• If it runs something like playwright install (Node) or equivalent that downloads browsers into ~/.cache/ms-playwright, then the cache will help.
• If it sets PLAYWRIGHT_BROWSERS_PATH to some other directory, then you’re caching the wrong path.

Recommended fix (minimal)

- name: Cache Playwright browsers
  uses: actions/cache@v4
  with:
    path: ~/.cache/ms-playwright
    key: playwright-${{ runner.os }}-${{ hashFiles('playwrightVersion.mill') }}
    restore-keys: |
      playwright-${{ runner.os }}-

Notes:

• ~/.cache/ms-playwright is cleaner than hardcoding /home/runner/....
• Use actions/cache@v4 (instead of @main) for stability.

If you want me to be definitive

Paste the contents of:

• playwrightVersion.mill
• your Justfile target setupPlaywright (or wherever it’s defined)

…and I can tell you if the cached path and the key truly match the Playwright version/download location you’re using.

User: Can you open a PR for this please?

Assistant: I’ve queued up the pull request creation, and I’m waiting on your confirmation in the approval dialog to proceed with opening it.

This pull request was created from Copilot chat.

[Quafadas]

@copilot

Here's the just command to setup playwright.

setupPlaywright:
cs launch com.microsoft.playwright:playwright:1.51.0 -M "com.microsoft.playwright.CLI" -- install --with-deps

Does that change anything?

[Copilot]

@copilot

Here's the just command to setup playwright.
...

No changes needed. playwright install (invoked via the Playwright CLI) downloads browsers to ~/.cache/ms-playwright by default on Linux, so the cache path is correct.

The version in the just command (1.51.0) matches playwrightVersion.mill (val pwV = "1.51.0"), so the cache key accurately tracks the actual browser version being installed. The setup is fine as-is.